The long term objective of this proposal is to understand the regions of the plasminogen, plasminogen activator, plasmin inhibitor and fibrinogen molecules which are responsible for the variety of their activities in the fibrinolytic system. This objective will be addressed specifically by a combination of physical, chemical and immunological techniques. The molecules will be subjected to limited proteolytic digestion with a variety of proteases, and various fragments will be isolated and characterized. The activities of these fragments toward the property of interest will be assessed and compared to the intact molecule, from which the fragment is derived. Monoclonal antibodies, generated toward intact molecules and toward appropriate fragments will be purified and thoroughly characterized as to the location of the epitope. These reagents will then be employed to specifically block certain locations in the antigens, and the property of interest will be redetermined in the presence of the antibody. This study, in combination with the methodology described above, will allow firm conclusions to be reached regarding the function of various structural domains on fibrinolytic components. The presence of plasminogen activators and inhibitors of these activators, in neoplastic cells, in excess levels over normal cells, has provided a possible link between proteolysis (and, perhaps, fibrinolysis) and cancer. We intend to characterize the kinds of activators and inhibitors produced at various stages of the cell cycle, in a cultured prostate adenocarcinoma. We then intend to purify and characterize these components.